The main objective of this study is to determine if omega 3 polyunsaturated fatty acids (pufas) can slow the accumulation of brain MRI derived white matter hyperintensities (WMH) over 3 years in a population at risk for dementia by advanced age, evidence of WMH and lower pufa status. This pilot trial is designed to collect preliminary data on pufa effects on total WMH progression, plasma biomarkers of endothelial function and rate of cognitive change over time. The study is a randomized, double-blind, placebo-controlled trial. Non- demented elders age 80 and older with WMH burden and lower plasma pufas will be enrolled. One hundred and fifty subjects will be randomized, half to pufa supplementation, and half to placebo over a 3 year term. Aim 1 will assess the effects of this nutritional therapy on WMH progression. Our hypothesis is that those randomized to pufas will appreciate less WMH progression. Aim 2 will assess the pufa effects on biomarkers of endothelial function as a potential modulator of the effects on total WMH and cognitive change. We hypothesize that pufas improve biomarkers of endothelial function. Aim 3 will collect preliminary data on the change in executive function and processing skills to inform the more definitive prevention trials in the future. We hypothesize that pufas slow vascular pathology mediated cognitive aging.